THE SELECTION MECHANISM OF PHOSPHINOTHRICIN IS INFLUENCED BY THE METABOLIC STATUS OF THE TISSUE

In a study to optimize the use of the bar gene as a selectable marker gene in plant transformation, the selection mechanism of phosphinothri cin in vitro was studied. It was found that tissues with a high anabol ic activity were more sensitive to the toxicity of ammonium than tissu es with a low anabolic activity. However, tissues with a low anabolic and high catabolic activity were more sensitive to glutamine deprivati on. The metabolic (anabolic and catabolic) activity of callusing hypoc otyl explants of Brassica napus L. was influenced by the carbon source of the medium and the light condition. The expression of the bar gene regulated by the light-inducible promoter derived from the gene codin g for the small subunit of ribulose-1,5-bisphosphate carboxylase-oxyge nase was also influenced by both light condition and carbon source. Fi nally, a bioassay to screen for, and to quantify the resistance of exp lants to, phosphinothricin is presented.